1. Field of the Invention
This invention relates to a high volumetric energy density battery having a light metal anode, a blended cathode active material and a non-aqueous electrolytic solution. The exothermic reactivity of the anode material with water requires the use of a non-aqueous, organic solvent containing a dissolved salt as the electrolytic solution. The electrochemical system provides a very high volumetric energy density, and it is generally preferred to employ the system in small primary batteries in order to reduce the fire hazard. The invention is not limited to any particular battery size or construction, nor is it limited to any particular anode material or non-aqueous electrolyte.
2. Description of the Prior Art
The prior art discloses many high energy density battery systems which employ a light metal anode in combination with a non-aqueous, organic electrolyte solution. Of particular relevance are U.S. Pat. Nos. 3,658,592 issued to A. N. Dey and 3,736,184 issued to A. N. Dey and R. W. Holmes, both assigned to P. R. Mallory & Co., Inc. and U.S. Pat. Nos. 3,853,627 and 3,871,915, both assigned to Societe des Accumulateurs Fixes et de Traction.
U.S. Pat. No. 3,658,592 discloses a high energy density organic electrolyte battery employing a light metal anode and a metal chromate cathode. The cathode contains a conductive ingredient such as graphite and a polymeric binder such as polytetrafluoroethylene mixed with the metal chromate active material. The cathode composition is molded onto an expanded metal current collector. The patent discloses that the lithium-silver chromate cell had an open circuit voltage of 3.5 and an average operating voltage of 2.4, presumably in an electrolyte solution comprising lithium perchlorate (LiClO.sub.4) and tetrahydrofuran (THF).
U.S. Pat. No. 3,736,184 discloses a high energy density, organic electrolyte battery employing a light metal anode and a metal phosphate cathode. The cathode contains a conductive ingredient such as graphite and a polymeric binder such as polytetrafluoroethylene mixed with the metal phosphate active material. The cathode composition is molded onto an expanded metal current collector. The patent discloses that the lithium-silver phosphate cell had an open circuit voltage of 3.5 and an average operating voltage of 2.8, presumably in an electrolyte solution comprising lithium perchlorate dissolved in tetrahydrofuran.
U.S. Pat. No. 3,853,627 issued to Gerard Lehmann and Jean-Paul Gabano discloses a high energy density system employing a lithium anode in which the cathode is selected from silver chromate (Ag.sub.2 CrO.sub.4) and lead chromate. The preferred electroytic solution comprises lithium perchlorate dissolved in a solvent mixture such as tetrahydrofuran and dimethoxyethane. The cells had an average discharge voltage of 2.95v. across a 9100 ohm resistor and a 3.15v. discharge across a 62,000 ohm resistor. The cathode contained 1% by weight carbon black as a conductor.
U.S. Pat. No. 3,871,915 issued to Alfred Brych discloses a high energy density lithium cell in which the cathode is selected from copper oxide or silver chromate. The preferred electrolyte comprises lithium perchlorate dissolved in a solvent comprising a mixture of a cyclic ether (dioxolane) and a non-saturated cyclic ester (vinylene carbonate). A cell having a silver chromate, graphite, polytetrafluoroethylene cathode and an 80% vinylene carbonate and 20% dioxolane electrolytic solution with a lithium anode had a two voltage plateau discharge across a 300 ohm resistor with voltage plateaus of 3v. and 2.6v.
High energy density, organic electrolyte batteries using lithium-silver phosphate and lithium-silver chromate systems have been investigated, and it has been determined that the silver phosphate active material provides very high volumetric energy density. However, there is a major problem with silver phosphate which expands substantially during discharge causing the battery or cell container to bulge severely. The lithium-silver chromate system causes less cell bulging, however, it has a lower volumetric energy density and a lower operating voltage than the silver phosphate system.